Deaeration and pumping of high pressure condensate



Sept. i9, w67 G. W. Ross 3,342,029

DEAERATION AND PUMPING OF HIGH PRESSURE CONDENSATE Filed Nov. 28, 196e 7 0 B0/ EE Fff WW 257.1572747 ATTORNEYS ttes 3,342,020 DEAERATION AND PUMPING OF HiGH PRESSURE CONDENSATE Gene W. Ross, Lorain, Ohio, assigner, by mesne assignments, to Ritter Pfaudler Corp., Rochester, N.Y., a corporation of New York Filed Nov. 28, 1966, Ser. No. 597,386 3 Claims. (Cl. 5S-164) ABSTRACT OF THE DISCLOSURE This invention relates to equipment for collecting, deaerating and returning steam condensate to a boiler feed water system and in particular to equipment for deaerat- Ving and pumping condensate which is initially at superatmospheric pressure and above its atmospheric 'boiling point. In the preferred embodiment the apparatus includes a single tank which is divided by a transverse partition into an upper flash chamber and a lower storage chamber, and means are provided for removing accumulated heavy gases from the flash chamber.

Disclosure Amore easily handled by the condensate pumping equipment than is the initial high pressure, high temperature condensate, The pressure at which the initial condensate is flashed may be at atmospheric pressure, somewhat higher than atmospheric pressure or subatmospheric pressure.

The use of a conventional flash tank alone is uneconomical, because the steam which is formed by the flashing process is lost and thereby eifects a heat loss from the system. For example, the steam produced in flashing condensate from 2O p.s.i.g. to 0 p.s.i.g. represents 4.9% of the 'heat input to the flash tank. To offset this disadvantage some systems include a supplementary tank which receives the low pressure condensate fro-m the ash tank and special valving and piping interconnecting the supplementary tank with a high pressure steam line leading from the boiler. The arrangement is such that the high pressure steam periodically pressurizes the supplementary tank to force low pressure condensate to the boiler feed water system. The pressurizing steam in the tank is then allowed to pass to the ash tank where a higher percentage of it is lost through a relief valve.

In operation of the above-described conventional system the incoming high pressure condensate is initially deaerated in the ash tank due to the boiling-point condition of the liquid remaining after ashing. This deaeration feature is known, because it is recognized in the art that dissolved gases come out of solution when the liquid is at its boiling point and that the liberated gases pass out of the flash tank vent. It has now been found, however, l

that the conventional system is prone to allow redissolution of the liberated gas with the result that the condensate which is returned to the boiler feed water system is very corrosive. Specifically, it has lbeen found that a layer of heavy gases, oxygen and more important carbon dioxide accumulates over a period of time just above the 3,342,2 Patented Sept. 19, 1967 liquid surface and to remain in the flash tank in spite of the venting of steam vapor. Over a long period of operation the carbon dioxide content of the layer increases until its concentration is much higher than its normal concentration in air. Due to its higher solubility in water than, for example, nitrogen, there is a marked tendency for the carbon dioxide to redissolve in the condensate. This is highly undesirable because the condensate becomes acidic due to the formation of carbonic acid and therefore corrosive to the feed water system, boiler and steam auxiliary equipment.

It is accordingly one object of the present invention to provide a high pressure condensate flash system having improved deaeration means for preventing the accumulation of heavy gases, particularly carbon dioxide, in the space above the condensate. It is a more specific object to provide compact, low cost equipment which performs the combined functions of flashing high pressure condensate to obtain low pressure condensate, removing heavy gases from the system, pumping the deaerated lower pressure condensate directly to the boiler feed Water system and at the same time minimizing heat losses due to flashing.

The invention will be further understood from the following description of an illustrative embodiment taken with the drawing in which:

FIGURE l is a Vertical cross sectional view of a combined flash tank, deaerator and pumping system for use in handling high pressure steam condensate; and

FIGURE 2 is a diagrammatic View, on a reduced scale, of a steam boiler system employing the equipment shown in FIGURE 1.

The condensate handling unit of the present invention, illustrated at 10, is constructed in the form of a single shell 12 having partition 14 dividing the interior of the shell 12 into an upper chamber 16 and a lower chamber 18. The upper chamber 16 functions as a flash chamber for high pressure condensate and in addition provides for collection and removal of gases from the system. The lower chamber 18 Collects low pressure condensate from the upper chamber 16 and periodically returns it to a boiler feed water system. The term highpressure condensate is employed to identify condensate which is at superatmo-shperic pressure and above 212 F. In the illus- 'I auxiliary equipment are required. The unit may be employed as original equipment in the boiler system or it may be substituted for the conventional flash tank, for the conventional ash tank plus auxiliary tank referred to previously or for a motor-pump condensate transfer system.

A typical steam boiler system is illustrated diagrammatically in FIGURE 2 as including a boiler feed water pumping 'system 25, a boiler house 26, a high pressure steam line 28 leading from the boiler 2'6, steam consumption equipment 30, and a high pressure condensate line 32 which contains a steam trap t31 or control oritice. The structure and operation of the steam boiler system are of no significance insofar as the present invention is concerned and need not be described. The boiler system is illustrated merely to indicate the environment in which the unit 10 is employed in practice.

Referring to FIGURE l, the condensate inlet means for the unit includes an inlet pipe 34 which extends from the flanged connection 20 into the lower portion of the flash chamber 16 where it terminates in a dilfuser head 36. A check valve 38 in the inlet pipe 34 prevents flow of condensate back into the line 32. The diffuser head 36 serves to distribute the incoming high pressure condensate within the body of condensate `40 in the flash chamber 16 and to permit more efficient heat transfer by mixing contents of the chamber 16.

A special vent arrangement is associated with the ash chamber 16 to elfect the necessary reduction in pressure and to assure that heavy gases will not accumulate in a layer above the condensate 40. The arrangement includes a conventional thermostatic steam trap 42 or other device which is adapted to pass liquid and gas but not steam. The device may be of the thermostatic type, as shown, or of the float or bucket type or of the thermodynamic type. In any case, the device is carried at the end of a tube 44 which extends through the shell 12 for connection with a heavy gas skimmer unit 46. Preferably the tube 44 is associated with a cooling device which condenses steam thereby creating a differential pressure across the ends of the tube. The cooling -device may be a simple heat eX- changer, such as an inverted 'U-'bend 49 having radial tins. If desired, a fan 43 may be provided for blowing air over the ns. An adjustable pressure relief valve 47 is provided in the tube 44 to prevent pressures higher than desired from building up in the chamber 16.

The skimmer unit 46 is arranged to skim gas from the surface of the condensate 40 and, in the illustrated embodiment, includes a oating funnel-like element 48 connected to the vent tube 44 by means of a flexible hose 50. The funnel-like element 48 is buoyantly supported by one or more floats 52 so that it remains just above the surface at any condensate level. The structure of the skimmer 46 may vary in size and shape, the primary criterion for its construction being that it vents gas from immediately above the surface of the condensate 40 in preference to steam vapor which resides substantially above the condensate 40. In large installations it may be desirable to employ more than one skimmer 46.

Low pressure condensate 40 is conducted by gravity out of the flash chamber 16 through a line '54 which extends laterally from about the midportion of the chamber '16 and then downwardly. Near the bottom of the chamber E18 the line '54 branches, one branch 56 leading to the chamber 18 and the other branch 58 leading to the boiler feed water system connection 22. Upstream of the junction the line 54 contains a check valve 60 which permits condensate flow only in a direction out of the flash chamber 16. Downstream of the junction the branch 58 contains a check valve 62 which permits condensate flow only in a direction toward the boiler 26.

High pressure steam from the boiler system is periodically made available to the chamber 18 through a line 66 for the purpose of forcing condensate I64 out through the lines 56 and 58. Steam is supplied to the line 66 by a line 68 from the boiler 26 through the connection 24. A normally closed valve 70` in the line 66 controls the ow of steam into the chamber I18.

The lines 34 and 66 are interconnected by a line 72 containing a check valve 73 and a normally open valve 74. When steam is flowing in the line 66, the valve 74 is closed.

A liquid level sensing system, including probes 76 and 78 disposed in the chamber 1-8, is employed, together with a control circuit 180, to open and close the valves 70 and 74. The probe y76- is disposed in the upper part of the chamber y18 and is :arranged to open the valve 70 and to close the valve 74 when contacted by the condensate 64. The probe '78 is located below the probe 76 and is arranged to return the valve 7(1 to its normally closed position and to return the valve 74 to its normally open position when the condensate 64 drops.

In operation of the illustrated system high pressure condensate produced by condensation of steam in the equipment '30 passes into the line 32 through the trap 3'1 and then through the check valve 38, the line 34 and the diffuser 36 into the flash chamber 16 where it mixes with the condensate 40 which is Valready present. The relief valve 47 opens to maintain the pressure in the chamber 16 at the desired maximum pressure with the result that some of the condensate flashes to steam and the remaining condensate cools to its boiling temperature. The amount which flashes is that amount which in vaporizing absorbs the heat given up by the remaining condensate in cooling. Substantially complete deaeration occurs, and most of the liberated gases are collected and vented to atmosphere through the skimmer 46, the steam trap 42 and at periods of higher pressure through the relief valve 47. The open upper end of the skimmer 46, being continually disposed immediately above the condensate surface, assures that gas will be swept from the condensate surface thereby preventing the accumulation of a layer of heavy gases at this location. As described previously, this prevents the formation of a high carbon dioxide content atmosphere above the condensate and therefore eliminates redissolution of this 4gas in the condensate. Venting is assisted by the condensing action of the tube 49.

As the ash chamber 16 lls with condensate to the level of the upper end of the pipe 54, condensate flows by lgravity through the check valve 60 into the collection chamber '1.8. Upon activation of the upper liquid level probe 76 the control circuit z80 opens the valve 70 in the high pressure steam line 66 and closes the valve 74. High pressure steam enters the collection chamber 18 and forces the condensate therein through the check 62 and the pipe `58 to the boiler feed system. When the condensate level falls to the lower pro'be 718, the control circuit 80 closes the valve 70 and opens the valve 74. The steam in the collection chamber 1'8 then expands and ows through the valve 74, the lines 72 and 34, the diffuser 36 and into the condensate in the flash chamber 16. The introduction of this higher pressure steam through the diffuser 36 effects another deaeration of the condensate, because the latter is reboiled and mixed as the steam enters and condenses. At the same time gases are vented to atmosphere through the skimmer 46, as described previously with respect to the introduction of high pressure condensate. The condensation of the high pressure steam within the mass of condensate and subsequent flashing of the latter effects an advantage in that the incoming steam cannot vent directly to atmosphere; this conserves steam and assures that any Igas layer will be forced through the skimmer 46.

The yabove-described cycle repeats -as more high-pressure condensate enters the flash chamber 16.

While preferred embodiments of the present invention have been described, further modifications may be made without departing from the scope of the invention. Therefore, it is to be understood that the details set forth or shown in the drawings are to be interpreted in an illustrative, and not in a limiting sense, except as they appear in the appended claims.

What is claimed is:

1. A deaerator and pumping unit for high pressure steam condensate for use with a steam boiler feed system comprising: a tank having an internal partition dividing the interior of said tank into an upper chamber and a lower chamber; a steam condensate conduit communieating with said upper chamber for delivering condensate thereto; vent means associated with said upper chamber foimaintaining a desired pressure on the condensate and for removing noncondensible gases from said upper chamber, said vent means including a float carried by the surface of the condensate in said upper chamber and vertically movable with the surface, a vent conduit having an open end, said conduit carried by said oat in a position such that said open end is disposed just above the surface,

an adjustable pressure relief valve in said conduit, and means connected to the other end of said conduit to pass noncondensible gases and liquid to the atmosphere and to prevent passage of steam; conduit means for conducting condensate from the upper portion of said upper chamber t said lower chamber, said conduit means including oneway valve means permitting liquid ow only from said upper chamber to said lower chamber; conduit means for conducting condensate out of said lower chamber for return to the boiler, said conduit means including one-way valve means permitting liquid ow only from said lower chamber; means for introducing high pressure steam from the boiler into said lower chamber; means for introducing high pressure steam condensate into said upper chamber; and control means for said steam introducing means and for said condensate introducing means, said control means including a device associated with said lower chamber responsive to a predetermined high liquid level therein to simultaneously introduce high pressure steam into said lower chamber while closing said condensate introducing means and responsive to a predetermined low liquid level in said lower chamber to simultaneously close said steam introducing means and open said condensate introducing means.

2. Apparatus as in claim 1 wherein said control means includes a valve interconnecting said steam introducing means with said condensate introducting means and a valve in said steam introducing means upstream of said interconnecting valve and wherein said level responsive device closes said interconnecting valve and opens said upstream valve at said predetermined high liquid level and reverses said valves at said predetermined low liquid level.

3. Apparatus as in claim 1 including cooling means associated with said vent conduit for condensing steam in the latter so as to aid in drawing gases through said vent conduit, said apparatus further including diffuser means disposed in said upper chamber and connected to said steam condensate conduit whereby condensate enters said upper chamber through said diffuser means.

References Cited UNITED STATES PATENTS 3,104,163 9/1963 Baker 55-164 REUBEN FRIEDMAN, Primary Examiner. R. W. BURKS, Assistant Examiner. 

1. A DEAERATOR AND PUMPING UNIT FOR HIGH PRESSURE STEAM CONDENSATE FOR USE WITH A STREAM BOILER FEED SYSTEM COMPRISING: A TANK HAVING AN INTERNAL PARTITION DIVIDING THE INTERIOR OF SAID TANK INTO AN UPPER CHAMBER AND A LOWR CHAMBER; A STEAM CONDENSATE CONDUIT COMMUNICATING WITH SAID UPPER CHAMBER FOR DELIVERING CONDENSATE THERETO; VENT MEANS ASSOCIATED WITH SAID UPPER CHAMBER FOR MAINTAINING A DESIRED PRESSURE ON THE CONDENSATE AND FOR REMOVING NONCONDENSIBLE GASES FROM SAID UPPER CHAMBER, SAID VENT MEANS INCLUDING A FLOAT CARRIED BY THE SURFACE OF THE CONDENSATE IN SAID UPPER CHAMBER AND VERTICALLY MOVABLE WITH THE SURFACE, A VENT CONDUIT HAVING AN OPEN END, SAID CONDUIT CARRIED BY SAID FLOAT IN A POSITION SUCH THAT SAID OPEN END IS DISPOSED JUST ABOVE THE SURFACE, AN ADJUSTABLE PRESSURE RELIEF VALVE IN SAID CONDUIT, AND MEANS CONNECTED TO THE OTHER END OF SAID CONDUIT TO PASS NONCONDENSIBLE GASES AND LIQUID TO THE ATMOSPHERE AND TO PREVENT PASSAGE OF STEAM; CONDUIT MEANS FOR CONDUCTING CONDENSATE FROM THE UPPER PORTION OF SAID UPPER CHAMBER TO SAID LOWER CHAMBER, SAID CONDUIT MEANS INCLUDING ONEWAY VALVE MEANS PERMITTING LIQUID FLOW ONLY FROM SAID UPPER CHAMBER TO SAID LOWER CHAMBER; CONDUIT MEANS FOR CONDUCTING CONDENSATE OUT OF SAID LOWER CHAMBER FOR RETURN TO THE BOILER, SAID CONDUIT MEANS INCLUDING ONE-WAY VALVE MEANS PERMITTING LIQUID FLOW ONLY FROM SAID LOWER WAY VALVE MEANS PERMITTING LIQUID FLOW ONLY FROM SAID UPPER CHAMBER TO SAID LOWER CHAMBER; CONDUIT MEANS FOR ING HIGH PRESSURE STEAM CONDENSATE INTO SAID UPPER CHAMBER; AND CONTROL MEANS FOR SAID STEAM INTRODUCING MEANS AND FOR SAID CONDENSATE INTRODUCING MEANS, SAID CONTROL MEANS INCLUDING A DEVICE ASSOCIATED WITH SAID LOWER CHAMBER RESPONSIVE TO A PREDETERMINED HIGH LIQUID LEVEL THEREIN TO SIMULTANEOUSLY INTRODUCE HIGH PRESSURE STEAM INTO SAID LOWER CHAMBER WHILE CLOSING SAID CONDENSATE INTRODUCING MEANS AND RESPONSIVE TO A PREDETERMINED LOW LIQUID LEVEL IN SAID LOWER CHAMBER TO SIMULTANEOUSLY CLOSE SAID STEAM INTRODUCING MEANS AND OPEN SAID CONDENSATE INTRODUCING MEANS. 